Packet transmission in a wireless communication system using multiple antennas

ABSTRACT

A method of retransmitting packet data in a wireless communication system comprises receiving a link map information element from a transmitting station having three antennas to achieve space time transmit diversity, wherein first, second and third packet data are transmitted from first, second and third antenna of the transmitting station, respectively. The method also comprises transmitting a non-acknowledgement signal to the transmitting station if at least one packet data from the transmitting station is not properly decoded. The method also comprises receiving the packet data from the transmitting station, wherein at least two of retransmitted packet data are transmitted from different antennas of the transmitting station, and one of retransmitted packet data is transmitted from the same antenna of the transmitting station. The retransmitted packet data are received with an information element comprising a retransmission count associated with a number of retransmission made by the transmitting station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 11/205,816,filed on Aug. 17, 2005, now U.S. Pat. No. 7,554,985, issued on Jun. 30,2009, which pursuant to 35 U.S.C. §119(a), claims the benefit of earlierfiling date and right of priority to Korean Application No.2004-0064551, filed on Aug. 17, 2004, and Korean Application No.2005-0019788, filed on Mar. 9, 2005, the contents of which are herebyincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to a wireless communicationsystem and, more particularly, to packet transmission in a wirelesscommunication system.

BACKGROUND OF THE INVENTION

Multimedia services in wireless communication systems are in increasingdemand. Developments are being made to achieve data transmissions withhigher capacity and higher speed. Therefore, efficient use of limitedradio frequency resources is of increasing importance. To this end, amultiple-input multiple-output (MIMO) system using a multi-antenna hasbeen employed. The multi-antenna system uses two or four transmittingantennas to send packets.

FIGS. 1(A) and 1(B) depict mathematical representations (e.g., matrices)of an exemplary signal (e.g., packet) transmitted through two and fourtransmitting antennas, respectively. FIGS. 2(A) and 2(B) depictmathematical representations of an exemplary re-transmission packettransmitted through each antenna when initial transmission of the packetfails.

Referring to FIGS. 2(A) and 2(B), if an error occurs in packettransmission, the transmission system alters the packets to enable themto be transmitted through each antenna. The transmission thenre-transmits the packets. Such a re-transmission method may allow SNR(signal to noise ratio) gain at a receiving side to be increased bymaking an initially transmitted packet and a re-transmitted packet havea STTD (space time transmit diversity) structure.

However, the conventional packet re-transmission using two or fourtransmitting antennas may have problems, such as waste of radioresources.

Furthermore, in the field of data transmissions, an ARQ (AutomaticRepeat reQuest) method is a type of error data re-transmission method.ARQ refers to a response message that indicates whether or not areceiving station has properly received data after transmission. The ARQresponse method comprises three types: a Stop-and-wait ARQ, a Go-back-NARQ and a Selective-repeat ARQ.

FIG. 3(A) illustrates three types of ARQ methods.

Referring to FIG. 3(A), the Stop-and-wait ARQ is a method where atransmitting station transmits data and waits to receive an ACK(acknowledgement) or NACK (non-acknowledgement) message (signal) from areceiving station. Then, the transmitting station transmits new data orre-transmits the previously transmitted data. The Go-back-N ARQ is amethod where data is continuously transmitted regardless of receiving aresponse. When a NACK signal is received, data is re-transmitted in turnstarting from the data indicated by the NACK signal. TheSelective-repeat ARQ is a method where data is continuously transmitted,and only the data for which a NACK signal has been received isre-transmitted.

For packet data transmissions, in order to prevent errors that may begenerated in a high speed transmission environment employing a high datarate (e.g., 2 Mbps, 10 Mbps or higher), a suitable coding rate ormodulation method (e.g., Rc=5/6, 3/4; Mod=16-QAM, 64QAM) has beenapplied to communication systems. In addition to this, an ARQ methodsuitable for the high-speed transmission environment, namely, a HybridARQ (HARQ) method has been proposed.

In the ARQ method, when an error is generated, the correspondinginformation is discarded, whereas in the HARQ method, information withan error is stored in a buffer and combined with re-transmittedinformation and FEC (Forward Error Correction) is applied thereto. Thus,the HARQ method employs the ARQ method with FEC additionally performed(HARQ=FEC+ARQ).

The HARQ method may be divided into four types, as described below.

FIG. 3(B) shows a Type I HARQ method, by which an error detection codeis added to data in order to preferentially detect an FEC. If the data(packet) still includes an error, the transmitting station is requestedto re-transmit the data (packet). The packet with an error is discardedand the re-transmitted packet uses the same FEC code as that of thediscarded packet.

FIG. 3(C) shows a Type II HARQ method, which is also called an IR(Incremental Redundancy) ARQ. Referring to FIG. 3, according to the TypeII HARQ method, a first (initially) transmitted packet is not discardedbut is stored in a buffer and then combined with re-transmittedredundancy bits. Upon re-transmission, only the parity bits (excludingthe data bits) are re-transmitted. The parity bits that arere-transmitted are different for each re-transmission.

FIG. 3(D) shows a Type III HARQ method, which is a special case of theType II HARQ method. Here, each packet is self-decodable.Re-transmissions are performed for each packet that includes data aswell as portions having errors. Compared with the Type II HARQ method,the Type III HARQ method may achieve more accurate decoding, but hasless coding gain.

FIG. 3(E) shows a fourth method called ‘Type I with soft combiningmethod’, which combines the function of the Type I HARQ method plus afunction of storing the data first (initially) received from a receivingstation and combining such with re-transmitted data. The method is alsoreferred to as ‘metric combining’ or ‘chase combining.’ The method isadvantageous with respect to an Signal to Interference Plus Noise Ratio(SINR). Furthermore, the same parity bits for the re-transmitted dataare used.

The MIMO system will now be described as follows. The MIMO system is awireless system in which a terminal and a base station transmit andreceive signals using one or more antennas and diversity gain may beobtained on the time axis or on the frequency axis. The MIMO systememploys two types of methods: STTD (Space-Time Transmit Diversity) andCollaborative Spatial Multiplexing (SM). STTD is a method for obtainingdiversity gain through use of antennas and time axis information bytransmitting two or more signals via two or more antennas, whileCollaborative SM is a method for allocating two or more terminals to asingle radio resource.

For example, when the base station has two antennas, a MIMO matrix ‘A’of equation (1) shown below may be used to transmit signals S1 and S2according to the STTD method. Thus, equation (1) shows a MIMO matrix ofthe STTD method for 2-antenna transmission.

$\begin{matrix}{A = \begin{Bmatrix}S_{1} & {- S_{2}^{*}} \\S_{2} & S_{1}^{*}\end{Bmatrix}} & (1)\end{matrix}$

In equation (1), the rows of the matrix represent the signalssequentially transmitted through the first and second antennas, whilethe columns of the matrix refer to a time sequence. In other words, on afirst channel, the first antenna is used to transmit the signal S1 andthe second antenna is used to transmit the signal S2, while on thesecond channel, the first antenna is used to transmit the signal −S₂*and the second antenna is used to transmit the signal S₂. Assuming thatreception values received at the receiving end over time are r1 and r2,then r1 and r2 may be calculated by equation (2) shown below. Thus,equation (2) represents the reception signals for 2-antennatransmission:r ₁ =h ₁ ·S ₁ +h ₂ ·S ₂r ₂ =h ₁·(−S ₂*)+h ₂ ·S ₁*  (2)

In equation (2), h1 and h2 represent a channel state (condition orstatus) of the first and second antennas, respectively. In addition,when the base station has two antennas, in order to transmit the signalsS1 and S2 according to the Collaborative SM method, a MIMO matrix B,such as in equation (3) shown below may be used. Thus, equation (3)shows a MIMO matrix of the Collaborative SM method:

$\begin{matrix}{B = \begin{Bmatrix}S_{1} \\S_{2}\end{Bmatrix}} & (3)\end{matrix}$

In a communications system using three or four transmission antennas andperforming re-transmissions, when a first spatial multiplexingtransmission is performed, signals represented by the vectors shown in[Table 1] and [Table 2] are transmitted and each element of each vectoris transmitted via each antenna. [Table 1] shows an example of a HARQre-transmission vector when using three antennas, while [Table 2] showsan example of a HARQ re-transmission vector when using four antennas.Note: The tables are located on pages 6 and 7.

In this embodiment, when re-transmission is required, the odd numberedre-transmissions and the even numbered re-transmissions arediscriminated when performing re-transmissions. For an odd numberre-transmission, a re-transmission “option” (i.e., a type of space-timecode incremental redundancy for a matrix) may be selected such that oneof several re-transmission vectors is selectively used for there-transmission.

For the downlink, the information for selecting an option may beindicated by varying a codeword of a NACK signal that is received. Forexample, in case of ACK, the codeword “0,0,0” may be sent, while in caseof NACK, “4, 7, 2” may be sent to indicate Option 1, while “1, 2, 3” maybe sent to indicate Option 2, and “3, 6, 5” may be sent to indicateOption 3. In this manner, ACK and NACK may be distinguished, and in caseof NACK, the particular option to be used (Option 1, 2, or 3) may bedistinguished.

However, for the uplink, because the related art ACK/NACK signal isexpressed as a single bit, such option selection may not be indicated byusing the related art ACK/NACK signal.

TABLE 1 Odd number re- Even number re- Initial transmission transmissiontransmission Space time code incremental redundancy for matrix$S_{2}^{(0)} = \begin{bmatrix}S_{i + 1} \\S_{s + 2} \\S_{i + 3}\end{bmatrix}$ $S_{2}^{({odd})} = \begin{bmatrix}{- S_{i + 2}^{*}} \\S_{i + 1}^{*} \\S_{i + 3}^{*}\end{bmatrix}$ (Option 1) $S_{2}^{({even})} = \begin{bmatrix}S_{i + 1} \\S_{s + 2} \\S_{i + 3}\end{bmatrix}$ $S_{2}^{({odd})} = \begin{bmatrix}{- S_{i + 3}^{*}} \\S_{i + 2}^{*} \\S_{i + 1}^{*}\end{bmatrix}$ (Option 2) $S_{2}^{({odd})} = \begin{bmatrix}{- S_{i + 1}^{*}} \\S_{i + 3}^{*} \\S_{i + 2}^{*}\end{bmatrix}$ (Option 3)

TABLE 2 Odd number re- Even number re- Initial transmission transmissiontransmission Space time code incremental redundancy for matrix$S_{2}^{(0)} = \begin{bmatrix}S_{i + 1} \\S_{i + 2} \\\begin{matrix}S_{i + 3} \\S_{i + 4}\end{matrix}\end{bmatrix}$ $S_{2}^{({odd})} = \begin{bmatrix}{- S_{i + 2}^{*}} \\\begin{matrix}S_{i + 1}^{*} \\{- S_{i + 4}^{*}}\end{matrix} \\S_{i + 3}^{*}\end{bmatrix}$ (Option 1) $S_{2}^{({even})} = \begin{bmatrix}S_{i + 1} \\S_{i + 2} \\\begin{matrix}S_{i + 3} \\S_{i + 4}\end{matrix}\end{bmatrix}$ $S_{2}^{({odd})} = \begin{bmatrix}{- S_{i + 3}^{*}} \\\begin{matrix}{- S_{i + 4}^{*}} \\S_{i + 1}^{*}\end{matrix} \\S_{i + 2}^{*}\end{bmatrix}$ (Option 2) $S_{2}^{({odd})} = \begin{bmatrix}{- S_{i + 4}^{*}} \\\begin{matrix}{- S_{i + 3}^{*}} \\S_{i + 2}^{*}\end{matrix} \\S_{i + 1}^{*}\end{bmatrix}$ (Option 3)

As stated above, the related art MIMO system has at least the followingproblems. When re-transmission is performed, the field indicating the‘nth’ transmission is included in the Information Element (IE), but whenone of several options of the NACL signal is selected to be used insending a re-transmission vector, there is no definition or procedurethat specifies whether the base station or the terminal should performthe selection and then send the re-transmission vector, and there is nodefinition or procedure as to how such selection should be made.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to packet transmission ina wireless communication system that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

An object of the present invention is to provide for packet transmissionusing multiple transmitting antennas. The packet transmission maypreferably be a re-transmission. The multiple transmitting antennas maypreferably include three transmitting antennas.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, inone embodiment, a method of retransmitting packet data in a wirelesscommunication system comprises receiving a link map information elementfrom a transmitting station having three antennas to achieve space timetransmit diversity, wherein first, second and third packet data aretransmitted from first, second and third antenna of the transmittingstation, respectively. The method also comprises transmitting anon-acknowledgement signal to the transmitting station if at least onepacket data from the transmitting station is not properly decoded. Themethod also comprises receiving the packet data from the transmittingstation, wherein at least two of retransmitted packet data aretransmitted from different antennas of the transmitting station, and oneof retransmitted packet data is transmitted from the same antenna of thetransmitting station. The retransmitted packet data are received with aninformation element comprising a retransmission count associated with anumber of retransmission made by the transmitting station.

In the step of receiving the packet data from the transmitting station,retransmitted first packet data may be transmitted from the secondantenna, retransmitted second packet data is transmitted from the firstantenna, and retransmitted third packet data is transmitted from thethird antenna. The non-acknowledgement signal to the transmittingstation may comprise a retransmission option for informing thetransmitting station, the retransmission option being associated withantenna assignment of packet data retransmission.

The method may further comprise transmitting to the transmitting stationa link information element comprising a retransmission option forinforming the transmitting station, the retransmission option beingassociated with antenna assignment of packet data retransmission. Theretransmitted packet data may be conjugate of the originally transmittedpacket data. One retransmitted packet data may be transmitted with a 180degree phase shift from the originally transmitted packet data. The linkmap information element may comprise at least one of an uplink mapinformation element and a downlink map information element. Theoriginally transmitted packet data may be transmitted as follows:

$\quad\begin{bmatrix}S_{i + 1} \\S_{i + 2} \\S_{i + 3}\end{bmatrix}$and retransmitted packet data are transmitted as follows:

$\quad\begin{bmatrix}{- S_{i + 2}^{*}} \\S_{i + 1}^{*} \\S_{i + 3}^{*}\end{bmatrix}$

In another embodiment, a method of retransmitting packet data in awireless communication system comprises receiving a link map informationelement from a transmitting station having a plurality of antennas toachieve space time transmit diversity, wherein packet data aretransmitted from the plurality of antennas of the transmitting station,respectively. The method also comprises transmitting anon-acknowledgement signal to the transmitting station if at least onepacket data from the transmitting station is not properly decoded,wherein the non-acknowledgement signal to the transmitting stationcomprises a retransmission option for informing the transmittingstation, the retransmission option being associated with antennaassignment of packet data retransmission The method also comprisesreceiving the packet data from the transmitting station, wherein atleast two of retransmitted packet data are transmitted from differentantennas of the transmitting station. The retransmitted packet data arereceived with an information element comprising a retransmission countassociated with a number of retransmission made by the transmittingstation.

In yet another embodiment, a method of retransmitting packet data in awireless communication system comprises transmitting a link mapinformation element from a transmitting station to a receiving station,wherein the transmitting station comprises three antennas to achievespace time transmit diversity, wherein first, second and third packetdata are transmitted from first, second and third antenna, respectively.The method also comprises receiving a non-acknowledgement signal fromthe receiving station if at least one packet data is not properlydecoded. The method also comprises re-transmitting the packet data tothe receiving station, wherein at least two of retransmitted packet dataare transmitted through different antennas of the transmitting station,and one of retransmitted packet data is transmitted through the sameantenna of the transmitting station. The retransmitted packet data aresent with an information element comprising a retransmission countassociated with a number of retransmission made by the transmittingstation.

In still another embodiment, a method of retransmitting packet data in awireless communication system comprises transmitting a link mapinformation element from a transmitting station to a receiving stationhaving a plurality of antennas to achieve space time transmit diversity,wherein packet data are transmitted from the plurality of antennas ofthe transmitting station, respectively. The method also comprisesreceiving a non-acknowledgement signal from the receiving station if atleast one packet data from the transmitting station is not properlydecoded, wherein the non-acknowledgement signal from the receivingstation comprises a retransmission option for informing the transmittingstation, the retransmission option being associated with antennaassignment of packet data retransmission. The method also comprisestransmitting the packet data from the transmitting station to thereceiving station, wherein at least two of retransmitted packet data aretransmitted from different antennas of the transmitting station. Theretransmitted packet data are received with an information elementcomprising a retransmission count associated with a number ofretransmission made by the transmitting station.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings. It is to be understood that both the foregoinggeneral description and the following detailed description of thepresent invention are exemplary and explanatory and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIGS. 1(A) and 1(B) depict mathematical representations (e.g., matrices)of an exemplary signal (e.g., packet) transmitted through two and fourtransmitting antennas, respectively.

FIGS. 2(A) and 2(B) depict mathematical representations of an exemplaryre-transmission packet transmitted through each antenna when initialtransmission of the packet fails.

FIGS. 3(A) to 3(E) are diagrams illustrating various ARQ and HARQmethods.

FIG. 4 depicts a mathematical representation of an exemplary packet forinitial transmission using three antennas.

FIG. 5 depicts a mathematical representation of reception signals in areception system using three antennas.

FIGS. 6(A) to 6(D) depict mathematical representations of a packet forre-transmission using three antennas, according to various embodimentsof the present invention.

FIGS. 7(A) to 7(D) depict mathematical representations of receptionsignals in a reception system where packet re-transmission according tothe present invention is applied.

FIG. 8(A) is a block diagram illustrating an exemplary mobile stationfor use in conjunction with various embodiments of present invention.

FIG. 8(B) is a block diagram illustrating an exemplary network in whichvarious embodiments of the present invention may operate.

FIG. 9 is a diagram illustrating a data re-transmission procedure,according to an embodiment of the present invention.

FIG. 10 is a diagram illustrating a data re-transmission procedure,according to another embodiment of the present invention.

FIG. 11 is a diagram illustrating a data re-transmission procedure,according to yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The present invention may be embodied in a wireless communicationssystem such as the UMTS (Universal Mobile Telecommunications System)developed by the Third Generation Partnership Project (3GPP). However,the present invention may also be applied to communications systemsoperated using other specifications. Furthermore, the present inventionmay be implemented in an orthogonal frequency division multiplexing(OFDM)/orthogonal frequency division multiple access (OFDMA) system.However, the present invention may also be implemented in a wirelesscommunication system operated according to a different standard.Additionally, the mobile station referred to herein may be a userequipment (UE) or other type of mobile station.

Packet re-transmission after a failed initial packet transmission usingthree transmitting antennas is described herein. To this end,construction of a re-transmission packet to be transmitted through eachof the three antennas is disclosed. In the present invention, in atransmission system using three transmitting antennas, the threeantennas transmit packets si+1, si+2, and si+3, respectively, in a firsttransmission.

FIG. 4 depicts a mathematical representation (matrix) of an exemplarypacket (signal) for initial transmission using three antennas. Referringto FIG. 4, a reception system has at least three receiving antennas toreceive packets transmitted from the transmission system.

FIG. 5 depicts a mathematical representation of reception signals in areception system using three antennas. FIGS. 6(A) to 6(D) depictmathematical representations of a packet for re-transmission using threeantennas, according to various embodiments of the present invention.

Referring to FIG. 6(A), for packet re-transmission using three antennasaccording to a preferred embodiment of the present invention, first andsecond antennas exchange previous packets and a third antennare-transmits a different previous packet. Thus, three antennas transmittwo packets. For example, the first and second antennas transmit thesame packet, and the third antenna transmits a different packet.

Referring to FIGS. 6(B) and 6(C), for packet re-transmission using threeantennas according to additional preferred embodiments of the presentinvention, the first and second antennas exchange previous packets andthe third antenna re-transmits a new packet or does not transmit apacket. Thus, the first and second antennas transmit the same packet,and the third antenna transmits a different packet. More particularly,in the embodiment described with reference to FIG. 6(B), the packetinitially transmitted through the third antenna is receivedsuccessfully. The successful initial packet transmission using the thirdantenna may allow for more packets to be efficiently transmitted.

Referring to FIG. 6(D), an additional preferred embodiment of thepresent invention is described in which each antenna excludes itspreviously transmitted signal, and constructs a re-transmission packetby combining signals transmitted through other antennas. Such operationmay allow a receiving end to detect packets more efficiently while eachtransmitting antenna has the same power.

When the reception system receives the initial packet and/orre-transmitted packets according to the above embodiments, the receptionsignals may be represented by the matrices depicted in FIGS. 7(A) to7(D).

FIGS. 7(A) to 7(D) depict mathematical representations (matrices) ofreception signals in a reception system where packet re-transmissionaccording to the present invention is applied.

Referring to FIGS. 7(A) to 7(D), reception signals may be indicated as avector, as shown in the below formula.x=As+v

The reception system stores a transmission signal vector (s) from areception signal vector (x) and detects a signal transmitted from thetransmission system using a detection method, such as maximumlikelihood, MMSE (minimum mean-squared error) and/or zero-forcing.

Although the present invention is described with reference to threeantennas, the present invention may also be applied to more than fourantennas. As such, the above formula may be applied to more than fourreceiving antennas, and the packets may be transmitted and received in asimilar fashion to that described herein.

FIG. 8(A) is a block diagram illustrating an exemplary mobile stationfor use in conjunction with various embodiments of present invention.

Referring to FIG. 8(A), a block diagram of a mobile station 400 of thepresent invention is illustrated, for example a mobile phone forperforming the methods of the present invention. The mobile station 400includes a processing unit 410 such as a microprocessor or digitalsignal processor, an RF module 435, a power management module 406, anantenna 440, a battery 455, a display 415, a keypad 420, a storage unit430 such as flash memory, Read Only Memory (ROM) or Static Random AccessMemory (SRAM), a speaker 445 and a microphone 450.

A user enters instructional information, such as a telephone number, forexample, by pushing the buttons of a keypad 420 or by voice activationusing the microphone 450. The processing unit 410 receives and processesthe instructional information to perform the appropriate function, suchas to dial the telephone number. Operational data may be retrieved fromthe storage unit 430 to perform the function. Furthermore, theprocessing unit 410 may display the instructional and operationalinformation on the display 415 for the user's reference and convenience.

The processing unit 410 issues instructional information to the RFmodule 435, to initiate communication, for example, transmit radiosignals comprising voice communication data. The RF module 435 comprisesa receiver and a transmitter to receive and transmit radio signals. Theantenna 440 facilitates the transmission and reception of radio signals.Upon receiving radio signals, the RF module 435 may forward and convertthe signals to baseband frequency for processing by the processing unit410. The processed signals would be transformed into audible or readableinformation outputted via the speaker 445, for example.

The processing unit 410 is adapted to store message history data ofmessages received from and messages transmitted to other users in thestorage unit 430, receive a conditional request for message history datainput by the user, process the conditional request to read messagehistory data corresponding to the conditional request from the storageunit 430, and output the message history data to the display unit 415.The storage unit 430 is adapted to store message history data of thereceived messages and the transmitted messages.

FIG. 8(B) is a block diagram illustrating an exemplary network 1 inwhich various embodiments of the present invention may operate.

Referring to FIG. 8(B), a mobile station (e.g., UE) 2 is connected to acore network (CN) 4 through a UMTS terrestrial radio access network(UTRAN) 6. The UTRAN 6 configures, maintains and manages a radio accessbearer for communications between the UE 2 and the core network 4 tomeet end-to-end quality of service requirements.

The UTRAN 6 includes a plurality of radio network subsystems (RNS) 8,each of which comprises one radio network controller (RNC) 10 for aplurality base stations, or Node Bs 12. The RNC 10 connected to a givenbase station 12 is the controlling RNC for allocating and managing thecommon resources provided for any number of UEs 2 operating in one cell.One or more cells exist in one Node B 12. The controlling RNC 10controls traffic load, cell congestion, and the acceptance of new radiolinks. Each Node B 12 may receive an uplink signal from a UE 2 and maytransmit a downlink signal to the UE 2. Each Node B 12 serves as anaccess point enabling a UE 2 to connect to the UTRAN 6, while an RNC 10serves as an access point for connecting the corresponding Node Bs 12 tothe core network 4.

Among the radio network subsystems 8 of the UTRAN 6, the serving RNC 10is the RNC managing dedicated radio resources for the provision ofservices to a specific UE 2 and is the access point to the core network4 for data transfer to the specific UE. All other RNCs 10 connected tothe UE 2 are drift RNCs, such that there is only one serving RNCconnecting the UE to the core network 4 via the UTRAN 6. The drift RNCs10 facilitate the routing of user data and allocate codes as commonresources.

In one embodiment, a method of retransmitting packet data in a wirelesscommunication system comprises receiving a link map information elementfrom a transmitting station having three antennas to achieve space timetransmit diversity, wherein first, second and third packet data aretransmitted from first, second and third antenna of the transmittingstation, respectively. The method also comprises transmitting anon-acknowledgement signal to the transmitting station if at least onepacket data from the transmitting station is not properly decoded. Themethod also comprises receiving the packet data from the transmittingstation, wherein at least two of retransmitted packet data aretransmitted from different antennas of the transmitting station, and oneof retransmitted packet data is transmitted from the same antenna of thetransmitting station. The retransmitted packet data are received with aninformation element comprising a retransmission count associated with anumber of retransmission made by the transmitting station.

In the step of receiving the packet data from the transmitting station,retransmitted first packet data may be transmitted from the secondantenna, retransmitted second packet data is transmitted from the firstantenna, and retransmitted third packet data is transmitted from thethird antenna. The non-acknowledgement signal to the transmittingstation may comprise a retransmission option for informing thetransmitting station, the retransmission option being associated withantenna assignment of packet data retransmission.

The method may further comprise transmitting to the transmitting stationa link information element comprising a retransmission option forinforming the transmitting station, the retransmission option beingassociated with antenna assignment of packet data retransmission. Theretransmitted packet data may be conjugate of the originally transmittedpacket data. One retransmitted packet data may be transmitted with a 180degree phase shift from the originally transmitted packet data. The linkmap information element may comprise at least one of an uplink mapinformation element and a downlink map information element. Theoriginally transmitted packet data may be transmitted as follows:

$\quad\begin{bmatrix}S_{i + 1} \\S_{i + 2} \\S_{i + 3}\end{bmatrix}$and retransmitted packet data are transmitted as follows:

$\quad\begin{bmatrix}{- S_{i + 2}^{*}} \\S_{i + 1}^{*} \\S_{i + 3}^{*}\end{bmatrix}$

In another embodiment, a method of retransmitting packet data in awireless communication system comprises receiving a link map informationelement from a transmitting station having a plurality of antennas toachieve space time transmit diversity, wherein packet data aretransmitted from the plurality of antennas of the transmitting station,respectively. The method also comprises transmitting anon-acknowledgement signal to the transmitting station if at least onepacket data from the transmitting station is not properly decoded,wherein the non-acknowledgement signal to the transmitting stationcomprises a retransmission option for informing the transmittingstation. The retransmission option is associated with antenna assignmentof packet data retransmission. The method also comprises receiving thepacket data from the transmitting station, wherein at least two ofretransmitted packet data are transmitted from different antennas of thetransmitting station. The retransmitted packet data are received with aninformation element comprising a retransmission count associated with anumber of retransmissions made by the transmitting station.

In yet another embodiment, a method of retransmitting packet data in awireless communication system comprises transmitting a link mapinformation element from a transmitting station to a receiving station,wherein the transmitting station comprises three antennas to achievespace time transmit diversity, wherein first, second and third packetdata are transmitted from first, second and third antenna, respectively.The method also comprises receiving a non-acknowledgement signal fromthe receiving station if at least one packet data is not properlydecoded. The method also comprises re-transmitting the packet data tothe receiving station, wherein at least two of retransmitted packet dataare transmitted through different antennas of the transmitting station,and one of retransmitted packet data is transmitted through the sameantenna of the transmitting station. The retransmitted packet data aresent with an information element comprising a retransmission countassociated with a number of retransmissions made by the transmittingstation.

In still another embodiment, a method of retransmitting packet data in awireless communication system comprises transmitting a link mapinformation element from a transmitting station to a receiving stationhaving a plurality of antennas to achieve space time transmit diversity,wherein packet data are transmitted from the plurality of antennas ofthe transmitting station, respectively. The method also comprisesreceiving a non-acknowledgement signal from the receiving station if atleast one packet data from the transmitting station is not properlydecoded, wherein the non-acknowledgement signal from the receivingstation comprises a retransmission option for informing the transmittingstation. The retransmission option is associated with antenna assignmentof packet data retransmission. The method also comprises transmittingthe packet data from the transmitting station to the receiving station,wherein at least two of retransmitted packet data are transmitted fromdifferent antennas of the transmitting station. The retransmitted packetdata are received with an information element comprising aretransmission count associated with a number of retransmission made bythe transmitting station.

The present invention may provide for packet re-transmission using thethree transmitting antennas. As such, the present invention may providebetter performance than a re-transmission method based on a field entrycondition for obtaining error probability. The present invention may beparticularly suitable for low speed environments.

The transmitting station may be, for example, a base station or a mobilestation. Similarly, the receiving station may be, for example, a mobilestation or a base station. The various embodiments of the presentinvention may be applied to downlink and/or uplink transmission.

The present invention may also relate to an Information Element (IE)used for selecting a re-transmission vector. That is, the presentinvention relates to adding information into the IE to indicate the typeof re-transmission vectors being used by the MIMO system that employs aHARQ method.

Cases of when IE information is transmitted on the uplink and on thedownlink are described with reference to FIGS. 9 to 11, below.

FIG. 9 shows a data re-transmission procedure in accordance with a firstembodiment of the present invention. As shown, the base station uses anInformation Element (IE) to inform the terminal about data to betransmitted in order to receive a signal from the terminal (step S10).The terminal then transmits corresponding data to the base station (stepS20) and the base station receives such data and determines whether thereceived data is an ACK or a NACK.

If the received signal is a NACK, that is, if the received data has anerror, the base station transmits a NACK signal and an IE to theterminal (step S30). In such case, the base station may inform theterminal, by means of the IE, about the NACK signal by using a singlebit and about which re-transmission vector is to be used. Then, theterminal performs re-transmission accordingly (step S40).

The second and third embodiments of the present invention showsituations of a downlink HARQ data transmission.

FIG. 10 shows a data re-transmission procedure in accordance with asecond embodiment of the present invention. The base station transmitsfirst data and an IE to the terminal (step S110). Here, the IE has adefault value representing a particular re-transmission option.

After the initial (first) data arrives at the terminal, if the data hasan error, the terminal selects one of the re-transmission options andtransmits to the base station, a NACK signal according to the selectedoption (step S120).

Upon receiving the NACK signal from the terminal, the base stationincludes the received NACK option information into the IE in order toinform the terminal about which option the NACK signal (received by thebase station) belongs to, and transmits the IE (containing the receivedNACK option information) when sending the subsequent (second)re-transmission data. Here, the NACK option information is used toprovide re-confirmation to the terminal regarding the signal that theterminal had transmitted.

FIG. 11 shows a data re-transmission procedure in accordance with athird embodiment of the present invention. The base station selects aNACK option that is to be transmitted by a terminal, and then, transmitssuch to the terminal (step S210). That is, the base station determines aNACK signal of a certain option to be transmitted by the terminal if thedata contains an error, and adds the determined option information tothe IE. The base station then transmits the IE to the terminal togetherwith the data.

When the data from base station arrives and if such data is detected tocontain an error, the terminal transmits to the base station, the NACKsignal of the option that had been designated the base station (stepS220). Thereafter, when different data are transmitted, the base stationincludes the previously determined option information in the IE andtransmits it to the terminal (step S230).

The following Tables show exemplary formats of the Information Element(IE) that may be applied to various embodiments of the presentinvention. It should be noted that each IE according to the presentinvention may include a re-transmission option field.

[Table 3] shows a format of a MIMO Downlink Space-Time Code (DL STC)H-ARQ Sub-burst IE.

TABLE 3 MIMO_DL_STC_H-ARQ_Sub-Burst_IE { For (j=0; j<N sub-burst; j++) {Tx count 00: first transmission 01: second transmission 10: thirdtransmission 11: fourth transmission Retransmission Option 00: option1/default 01: option 2 10: option 3 11: reserved Length If (Tx count ==0 ) { MU Indicator . . . } } }

[Table 4] shows a format of a MIMO Uplink Space-Time Code (UL STC) H-ARQSub-burst IE.

TABLE 4 MIMO_UL_STC_H-ARQ_Sub-Burst_IE { Tx count 00: first transmission01: second transmission 10: third transmission 11: fourth transmissionRetransmission Option 00: option 1/default 01: option 2 10: option 3 11:reserved Duration If (Tx count == 0 ) { . . . } }

The packet re-transmission method in accordance with the presentinvention may have many advantages. For example, for the uplink (UL),when there is an error in the transmission data of the terminal, thebase station informs the terminal about a NACK bit and a re-transmissionvector by means of an Information Element (IE), such that the terminalmay select one of several re-transmission vectors and performsre-transmission accordingly.

For the downlink (DL), when the base station receives a NACK accordingto a specific option from the terminal, the base station providesconfirmation to the terminal by means of the Information Element (IE),and thus the possibility of errors that may be generated duringtransmission of the NACK signal may be reduced.

In addition, in the second method for the downlink, because the terminaldoes not select an option of the NACK, and instead, the base stationselects such option, complicated calculations that include thecalculation of a channel state (condition or status) may be preferablyperformed by the base station, such that the burden of the terminal dueto the option selection and power consumption of the terminal that wouldotherwise be required may be reduced.

Although the present invention is described in the context of mobilecommunication, the present invention may also be used in any wirelesscommunication systems using mobile devices, such as Personal DigitalAssistants (PDAs) and laptop computers equipped with wirelesscommunication capabilities. Moreover, the use of certain terms todescribe the present invention should not limit the scope of the presentinvention to certain type of wireless communication system, such asUMTS. The present invention is also applicable to other wirelesscommunication systems using different air interfaces and/or physicallayers, for example, Time Division Multiple Access (TDMA), Code DivisionMultiple Access (CDMA), Frequency Division Multiple Access (FDMA),Wideband Code Division Multiple Access (WCDMA), etc.

The preferred embodiments may be implemented as a method, apparatus orarticle of manufacture using standard programming and/or engineeringtechniques to produce software, firmware, hardware, or any combinationthereof. The term “article of manufacture” as used herein refers to codeor logic implemented in hardware logic (e.g., an integrated circuitchip, Field Programmable Gate Array (FPGA), Application SpecificIntegrated Circuit (ASIC), etc.) or a computer readable medium (e.g.,magnetic storage medium (e.g., hard disk drives, floppy disks, tape,etc.), optical storage (Compact Disc Read Only Memories (CD-ROMs),optical disks, etc.), volatile and non-volatile memory devices (e.g.,Electrically Erasable Programmable Read Only Memories (EEPROMs), ReadOnly Memories (ROMs), Programmable Read Only Memories (PROMs), RandomAccess Memories (RAMs), Dynamic Random Access Memories (DRAMs), StaticRandom Access Memories (SRAMs), firmware, programmable logic, etc.).

Code in the computer readable medium is accessed and executed by aprocessor. The code in which preferred embodiments are implemented mayfurther be accessible through a transmission media or from a file serverover a network. In such cases, the article of manufacture in which thecode is implemented may comprise a transmission media, such as a networktransmission line, wireless transmission media, signals propagatingthrough space, radio waves, infrared signals, etc. Of course, thoseskilled in the art will recognize that many modifications may be made tothis configuration without departing from the scope of the presentinvention, and that the article of manufacture may comprise anyinformation bearing medium known in the art.

The logic implementation shown in the figures described specificoperations as occurring in a particular order. In alternativeimplementations, certain of the logic operations may be performed in adifferent order, modified or removed and still implement preferredembodiments of the present invention. Moreover, steps may be added tothe above described logic and still conform to implementations of theinvention.

In the present invention, various retransmission options may beutilized. In a first option, first and second antennas are operativelyswitched for retransmission. In a second option, first and thirdantennas are operatively switched for retransmission. In a third option,second and third antennas are operatively switched for retransmission.Alternatively, other retransmission options may be used.

It will be apparent to those skilled in the art that variousmodifications and variations may be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of retransmitting packet data in a wireless communicationsystem, the method comprising: receiving a link map transmitted from abase station to a mobile station wherein the link map includes aninformation element for indicating retransmission option ofretransmitted data from the mobile station; and re-transmitting packetdata to the base station from the mobile station having three antennasto achieve space time transmit diversity, wherein first, second andthird packet data are respectively transmitted from first, second andthird antennas of the mobile station and the retransmitted packet dataare transmitted according to one of the following mathematicalrepresentations dependent on the retransmission option:${\begin{bmatrix}s_{i + 1} \\s_{i + 2} \\s_{i + 3}\end{bmatrix}\mspace{14mu}\begin{bmatrix}{- s_{i + 2}^{*}} \\s_{i + 1}^{*} \\s_{i + 3}^{*}\end{bmatrix}}.$
 2. The method of claim 1, further comprising: receivinga non-acknowledgement signal from the base station for indicating thatat least one packet data is not properly received.
 3. The method ofclaim 1, wherein the link map is a hybrid automatic repeat requestuplink map (HARQ UL-MAP).
 4. The method of claim 1, wherein theinformation element is a multiple-input multiple-output uplinkspace-time coding hybrid automatic repeat request sub-burst informationelement (MIMO UL STC HARQ sub-burst IE).
 5. A method of receiving packetdata in a wireless communication system, the method comprising:transmitting a link map from a base station to a mobile station whereinthe link map includes an information element for indicatingretransmission option of retransmitted data from the mobile station; andreceiving retransmitted packet data from the mobile station having threeantennas to achieve space time transmit diversity, wherein first, secondand third packet data are respectively transmitted from first, secondand third antennas of the mobile station and the retransmitted packetdata are transmitted according to one of the following mathematicalrepresentations dependent on the retransmission option:${\begin{bmatrix}s_{i + 1} \\s_{i + 2} \\s_{i + 3}\end{bmatrix}\mspace{14mu}\begin{bmatrix}{- s_{i + 2}^{*}} \\s_{i + 1}^{*} \\s_{i + 3}^{*}\end{bmatrix}}.$
 6. The method of claim 5, further comprising;transmitting a non-acknowledgement signal to the mobile station if atleast one packet data from the transmitting station is not properlyreceived.
 7. The method of claim 5, wherein the information element is amultiple-input multiple-output uplink space-time coding hybrid automaticrepeat request sub-burst information element (MIMO UL STC HARQ sub-burstIE).
 8. A mobile terminal used in a wireless communication system, themobile terminal comprising: a receiver configured to receive a link maptransmitted from a base station wherein the link map includes aninformation element for indicating retransmission option ofretransmitted data from the mobile terminal; and a transmitterconfigured to re-transmit packet data to the base station through threeantennas of the mobile terminal to achieve space time transmitdiversity, wherein first, second and third packet data are respectivelytransmitted from first, second and third antennas of the mobile terminaland the retransmitted packet data are transmitted according to one ofthe following mathematical representations dependent on theretransmission option: ${\begin{bmatrix}s_{i + 1} \\s_{i + 2} \\s_{i + 3}\end{bmatrix}\mspace{14mu}\begin{bmatrix}{- s_{i + 2}^{*}} \\s_{i + 1}^{*} \\s_{i + 3}^{*}\end{bmatrix}}.$
 9. The mobile terminal of claim 8, wherein the receiveris further configured to receive a non-acknowledgement signal from thebase station for indicating that at least one packet data is notproperly received.
 10. The mobile terminal of claim 8, wherein the linkmap is a hybrid automatic repeat request uplink map (HARQ UL-MAP). 11.The mobile terminal of claim 8, wherein the information element is amultiple-input multiple-output uplink space-time coding hybrid automaticrepeat request sub-burst information element (MIMO UL STC HARQ sub-burstIE).
 12. A base station used in a wireless communication system, thebase station comprising: a transmitter configured to transmit a link mapto a mobile station wherein the link map includes an information elementfor indicating retransmission option of retransmitted data from themobile station; and a receiver configured to receive retransmittedpacket data from the mobile station having three antennas to achievespace time transmit diversity, wherein first, second and third packetdata are respectively transmitted from first, second and third antennasof the mobile station and the retransmitted packet data are transmittedaccording to one of the following mathematical representations dependenton the retransmission option: ${\begin{bmatrix}s_{i + 1} \\s_{i + 2} \\s_{i + 3}\end{bmatrix}\mspace{14mu}\begin{bmatrix}{- s_{i + 2}^{*}} \\s_{i + 1}^{*} \\s_{i + 3}^{*}\end{bmatrix}}.$
 13. The base station of claim 12, wherein thetransmitter is further configured to transmit a non-acknowledgementsignal to the mobile station if at least one packet data from the mobilestation is not properly received.
 14. The base station of claim 12,wherein the information element is a multiple-input multiple-outputuplink space-time coding hybrid automatic repeat request sub-burstinformation element (MIMO UL STC HARQ sub-burst IE).